Apparatus for molding plastic articles



Dec. 12, 1967 N. R. REYBURN 3,357,056

APPARATUS FOR MOLDING PLASTIC ARTICLES Filed May 10, 1965 5 Sheets-Sheetl INVENTOR. NATHANlEL. R. REVBURN 310% M QLQ i Z). a.

Dec. 12, 1967 N. R. REYBURN 3,357,056

APPARATUS FOR MOLDING PLASTIC ARTICLES Filed May 10, 1965 5 Sheets-Sheet2 INVENTOR. 4 NATHANIEL R.REVBURN BY 6222 52 44 @zd ATTORNEVS Dec. 12,1967 N. R. REYBURN 3,357,056

APPARATUS FOR MOLDING PLASTIC ARTICLES Filed May 10, 1965 5 Sheets-Sheet5 INVENTOR.

NATHAN\EL R. REYBURN BY 6 jww ATTQRN QS r Dec. 12, 1967 N. R. REYBURN3,357,056

APPARATUS FOR MOL DING PLASTIC ARTICLES Filed May 10, 1965 5Sheets-Sheet 4 -INVENTOR. NAT HANI EL- R. REVBURN ATl-o RNEVS Dec. 12,1967 N. R. REYBURN 3,357,056

APPARATUS FOR MOLDING PLASTIC ARTICLES Filed May 10, 1965 5 Sheets-Sheet5 INVENTOR NATHANIEL RREVBURN United States Patent 3,357,056 APPARATUSFOR MOLDING PLASTIC ARTICLES Nathaniel R. Reyburn, Erie, Pa., assignorto Owens- Illinois, Inc., a corporation of Ohio Filed May 10, 1965, Ser.No. 454,472 1 Claim. (CI. 18-42) This case relates generally to anapparatus for molding plastic articles and more particularly tocompression molding double wall cup-shaped articles.

In the manufacture of plastic articles, such as cups and the like, it isfrequently desirable to mold the articles in two layers in order toprovide a two-color cup with the inside being one color and the outsidebeing another color. One method for molding this type of article isdisclosed in US. Reissue Patent No. 25,534, dated Mar. 10, 1964.

Heretofore, it has been necessary to use two sets of molds to formdouble wall cup-like articles. Thus, under the prior art the outer wallis molded in a female mold using one plunger and the inner wall ismolded therein using a second plunger. Under the present invention, itis possible to mold such articles using the same plunger to form boththe outer and the inner wall.

Accordingly, it is an object of the present invention to provide new andefficient apparatus for molding double wall plastic articles.

It is a further object of the present invention to provide an apparatusfor molding double wall cup-shaped plastic articles wherein a single setof molds is used for forming both the inner and the outer layers.

It is an additional object of the present invention to provide anapparatus for molding a plastic article having double walls andcharacterized in that the outer wall portion at the top or rim of thearticle is substantially thinner than the outer wall portion of theremainder of the article.

Other objects and advantages of the present invention will becomereadily apparent from the following detailed description taken inconjunction with the annexed sheets of drawings on which:

FIGURE 1 is an elevational view of one half of a partible female moldsection in which a handled cup-like article may be molded.

FIGURE 2 is a top plan view of the mold section illustrated in FIGURE 1.The other half of the partible female mold section is shown in dottedlines to illustrate a complete female mold section.

FIGURE 3 is a view similar to FIGURE 1 showing a plunger positioned inthe female mold section in position to mold the first layer of plasticwhich will form the outer or exterior wall and the handle of thearticle.

FIGURE 4 is a view similar to FIGURE 3 showing the plunger positioned tomold the second layer of plastic which forms the inner or interior wallof the article.

FIGURE 5 is a perspective view in section of a finished article formedaccording to the present invention.

FIGURE 6 is an enlarged fragmentary sectional view of the top or rimportion of an article formed according to the present invention prior totrimming the excess material therefrom.

FIGURE 7 is an enlarged fragmentary sectional view of a mold for forminga handleless article according to the present invention showing theplunger in position to mold the first layer of plastic forming the outerwall of the article.

FIGURE 8 is a view similir to FIGURE 7 showing the plunger in positionto mold the second layer of plastic forming the inner wall of thearticle.

3,357,056 Patented DecJlZ, 1967 Referring now to FIGURE 5, the articleto be molded according to the present invention is a cup generallydesignated by the letter C. If desired, the cup C may be provided with ahandle 3. The cup C includes a bottom 4 and an upwardly and outwardlyflaring sidewall 5 terminating at its upper end in an annular rim 6. Thecup C has an outer or exterior wall A which is formed during the moldingof the first layer of plastic molding compound and an inner or interiorwall B which is formed during the molding of the second layer of plasticmolding compound. For reasons which will become readily apparent fromthe following description, the upper portion of the sidewall 5 in thearea adjacent the top of the rim 6 is formed so that the exterior wall Ais substantially thinner than it is throughout the remainder of thesidewall 5. In contrast, the interior wall B in this area issubstantially thicker than it is throughout the remainder of thesidewall 5. For purposes of clarity the rim 6 should be understood tomean the entire area of the sidewall having the thinner exterior wall Aand the thicker interior wall B. The exterior wall portion of the rim 6is hereinafter referred to as the lip 7 and the interior wall portion ofthe rim 6 is hereinafter referred to as the shoulder 8.

As shown in FIGURE 6, the cup C is formed with an excess or wasteportion 9 which is removed in a separate operation by trimming flushwith the top of the shoulder 8.

Referring now to the other figures, the apparatus for forming the cup Ccomprises a female mold section generally designated by the numeral 10comprising partible halves 10' and 10 which cooperate to define a cavityhaving a molding surface corresponding to the desired externalconfiguration of the article to be molded. A plunger generallydesignated by the numeral 20 is sized to be received within the cavityof the female mold section 10. The plunger has an external moldingsurface having a configuration corresponding to the desired interiorconfiguration of the article to be molded.

The female mold section 10 has a cavity defined by a bottom wall 12 andan annular sidewall 14 which tapers upwardly and outwardly from thebottom wall 12. If desired, the mold section 10 may be formed with aconvex transition area 16 between the bottom wall 12 and sidewall 14.The sidewall '14 terminates at the upper end in a radially-outwardlydirected ledge 18. Extending upwardly from the ledge 18 is a verticalwall portion 22 which is parallel to the longitudinal axis of thecavity. Inasmuch as the cavity of the mold section 10 illustrated inFIGURES 1 through 4 has a circular cross-sectional configuration, thesidewall 14 defines a frustum of a cone and the vertical wall portion 22defines a cylinder. However, it should be understood that it is withinthe contemplation of the present invention that other crosssectionalconfigurations could be used. Additionally, the mold section 10 isprovided with a handle cavity 24 in which the handle 3 of cup C ismolded. It is because of the handle cavity 24 that the mold section 10is formed with partible halves 10' and 10". Upon completion of themolding operation the halves 10' and 10" are opened to permit removal ofthe handled cup C from the mold section 10. Any desired power means (notshown) may be utilized for opening and closing the partible halves 10and '10".

In order to assure that the partible halves 10' and 10" are preciselyaligned upon closing, it is desirable to form the one half 10' with atapered tongue 26 sized to be received in a corresponding groove 28 ofthe mating half 10". Referring to FIGURES 7 and 8, where it is desiredto form a handleless cup, it is preferred to form the female moldsection 10 as a unitary non-partible unit.

The plunger 20 has a substantially horizontal bottom molding surface 32,and a first annular sidewall 34 which tapers upwardly and outwardlysubstantially parallel to the sidewall 14 of mold section 10. The bottommolding surface 32 and the first annular sidewall 34 are joined by aradius portion 36. Additionally, there is provided a second taperingannular sidewall portion 38 and a third tapering annular sidewallportion 39. The second tapering annular sidewall 38 is above andradially outwardly from the first annular sidewall 34 and is joinedthereto by a first radially outwardly extending ledge 40. Similarly, thethird tapering annular sidewall 39 is above and radially outwardly fromthe second tapering annular sidewall 38 and is joined thereto by asecond radially outwardly extending ledge 41.

The plunger 20 has an upper sidewall 42 sized to be snugly received inthe vertical wall portion 22 of the female mold section 10. The uppersidewall 42 and the third tapering sidewall are joined by a thirdradially outwardly extending ledge 43. As shown in FIGURES 3 and 7, themold section and the plunger are sized so that the third sidewallportion 39 of the plunger substantially contacts the upper portion ofthe sidewall 14 upon the complete insertion of the plunger in the moldsection 10. The term substantially contact for the purpose of thisdescription is understood to mean that a very slight gap, on the orderof a few thousandths of an inch, may exist between the third taperingsidewall portion 39 and the sidewall 14 of mold section 10 when theplunger is fully inserted in said mold section, such gap being for thepurpose of permitting the escape of any excess plastic molding material;however, the gap is sufficiently small that substantial pressure buildsup upon the molding of the plastic material in order to completely fillthe molding cavity including handle cavity 24 in the case of theembodiment of FIGURES 1 through 4.

When the plunger 20 is fully inserted in the mold section 10, theseelements cooperate to define a molding cavity corresponding to thedesired configuration ofthe exterior wall and an overflow receivingchamber 46. See FIGURES 3 and 7.

FIGURES .4 and 8 illustrate the positioning of the plunger 20 withrespect to the mold section 10 during the molding of the second layer ofplastic forming the interior wall B.

It is desirable that none of the material used in forming the exteriorwall A be on the interior of the finished cup C and that none of thematerial used in forming the interior Wall E be on the exterior of thefinished .cup C. This is especially true where different color plasticis used for forming walls A and B. This feature is achieved by moldingthe second or inner layer forming interior wall B in accordance with thefollowing procedure. After the molding of the first layer wherein theplastic material fills the molding cavity forming the exterior wall A,with any excess flowing through the small gap between the third annularsidewall 39 of the plunger and the annular sidewall 14 of the mold intothe overflow receiving chamber 46, the plunger 20 is removed from themold 10, a second charge of molding compound is inserted in the mold 10on the first or exterior wall A and plunger 20 reinserted. The plunger20 is then lowered to a position such that the first radially outwardlyextending ledge is aligned axially with the lip 7 of the exterior wallA. In other words, the first radially outwardly extending ledge 40during the molding of the second or interior wall B is axially above theposition occupied by it during the molding of the first or exterior wallA but is below the position occupied by the second radially outwardlyextending ledge 41 during the molding of the first or exterior wall A.

Such positioning of the plunger 20 during the molding of the second orinterior wall B serves a multiple advantage. Firstly, it permits theattainment of the desired objective of providing a double wall cup inwhich one wall is confined solely to the exterior and the other isconfined solely to the interior while permitting the trimming operationto be accomplished by cutting through a relatively thin section ofplastic, thinner than the overall wall thickness of the finished cup.Thus, in the finishing operation wherein theexcess of waste portion 9 isremoved from the top of the cup C at the trim line (FIG. 6), it isnecessaryonly to cut through a section having a thickness, asillustrated in FIGURE 8, from the second annular sidewall 38 to the moldsidewall 14. In contrast, the attainment of the same objective wouldrequire cutting the full wall thickness extending from the first annularsidewall 34 to the mold sidewall 14 if thefirst radially outwardlyextending ledge 40 were positioned axially above the lip 7 during, themolding of the second or interior wall B. Additionally, the presentapparatus permits the trimming to be done precisely at the top of theshoulder 8 thereby taking advantage of the rounded or radiused cornermolded into the shoulder 8 at the .juncture of the sidewall 5 and thetop of the rim 6. Thus, ifthe trimming were done below the top of theshoulder 8, a separate bufiing operation would be required to remove thesharp corner on the inner edge of the rim resulting from such trimming.

As previously noted and as illustrated in FIGURES 3 and. 7, the moldingof the first or exterior wall A results in the excess plastic moldingcompound flowing. into the overflow receiving chamber 46. Inasmuch as.such excess is joined to the exterior wall A by a verythin section, onthe order of .a few thousandths inch corresponding to the gap betweenthe plunger third annular sidewall 39 and the mold section sidewall 14(FIGURES 3 and 7) it usually will be broken away from such exterior wallA during the molding of the second or interior .wall B. See FIGURES 6and 8.

It can be seen from the foregoing that the present .invention providesan efiicient and economical apparatus for-forming double wall cup-shapedarticles. Additionally, it provides an intermediate molded articlewhich. can be worked to the finished article with a minimum ofoperations, namely trimming with no necessity of buif or grinding theinner of the rim. Furthermore, it provides a double wall cup-shapedarticle in which the exterior wall at the rim is substantially thinnerthan the remainder of the exterior walllying in the sidewall area of thearticle.

I claim:

Apparatus for molding cup-shaped articles comprising a female moldsection having a cavity defined by abottom portion,

a flaring sidewall portion extending upwardly and outwardly from saidbottom portion,

a parallel sidewall portion upwardly and outwardly from said flaringsidewall portion, said parallel sidewall portion being parallel to theaxis of said cavity,

ashoulder extending outwardly from the upper end of said" flaringsidewall portion and joining said parallel sidewall portion,

a plunger sized to be received in said cavity in a first fully engagedposition for molding said outer layer and'asecondpartiallyengagedposition for moldingsaid inner layer, said plungerincluding first, second, and third sidewall'portions substantiallyparallel to said femalemold section flaring sidewall portion,

said second sidewall portion being upwardly and outwardly from saidfirst sidewall portion and joined. thereto by a first outwardlyextending ledge,

said third sidewall portionbeing upwardly and outwardly from said secondsidewall portion and joined thereto by a secondoutwardly extendingledge, said third sidewall portion sized tosubstantially contact saidfemale mold section flaringsidewallportion when the plunger is in thefirst fully engaged position,

5 said first outwardly extending ledge at said second partially engagedposition being axially below the position of said second outwardlyextending ledge at said first fully engaged position, an upper sidewallportion contoured to be snugly received in the parallel sidewall portionof said female mold section, said upper sidewall portion be ing upwardlyand outwardly from said third sidewall portion and joined thereto by athird outwardly extending ledge, said third sidewall portion and saidthird outwardly extending ledge cooperating with the parallel sidewallportion and shoulder of said female mold section to define an overflowreceiving chamber when the plunger is in the first fully engagedposition and when the plunger is in the second partially engagedposition.

References Cited UNITED STATES PATENTS Hobbs 249-58 X Rinley 249-58Brockunier 249-58 X Slick 249-58 X Taylor.

Couchman 18-5 X Northrup et al. 18-5 Kraus et a1. 18-5 Robbins et al.18-5 Bridges et a1. 18-5 X Dart 18-5 Schlitzkus 18-42 YOlin 18-42 Ludwig18-30 Kobayashi 249-83 XR Ludwig 18-30 XR J. HOWARD FLINT, JR., PrimaryExaminer.

